"one-off"

Funny...just looked at my internet banking this morning and the bank sent a message headed a "once-off announcement" I thought they made a mistake, admittedly unusual for them. Now I read here it is quite common. Is it more formal, as in financial or legal speak?? Never heard anyone say it...

I've never heard "once-off" or seen it for that matter. Sounds like either legal language or bureaucratic gobbledygook.

However, in any group even peripherally connected to manufactured goods, "one-off" is something immediately understood in U.S. English. The definition is exactly as nutrax has posted:

"A one-off was just a single item, used in particular to refer to a prototype. The first known example appeared in the Proceedings of the Institute of British Foundrymen in 1934: “A splendid one-off pattern can be swept up in very little time.” (The reference is to a casting mould formed in sand.)"

I've even heard it used in describing unique, designer clothing.

Used a lot in NZ, too. Most commonly to refer to production, but the meaning has expanded to cover payments, events etc.

It's used a lot in Australia.

yes, see No 13, ozzies use it frequently.